Final answer:
The mass percent of water in NiSO₄･4 H₂O is 32.75%.
Step-by-step explanation:
To find the mass percent of water in NiSO₄･4 H₂O, we need to determine the mass of water in the compound and divide it by the molar mass of the compound, then multiply by 100. The molar mass of NiSO₄･4 H₂O can be calculated by adding the molar masses of each element:
Molar mass of NiSO₄ = 58.7 g/mol + 32.1 g/mol + (4 * 16.0 g/mol) = 154.8 g/mol
Molar mass of H₂O = 2 * 1.0 g/mol + 16.0 g/mol = 18.0 g/mol
Therefore, the molar mass of NiSO₄･4 H₂O = 154.8 g/mol + (4 * 18.0 g/mol) = 218.8 g/mol.
The mass percent of water is then calculated as:
(4 * 18.0 g/mol) / 218.8 g/mol * 100% = 32.75%.